Today's different programming languages (FORTRAN, PL-1, ASSEMBLY, etc.) are often used interchangeably by operators at a common computer terminal for controlling a general purpose digital computer. The number, symbols and programming keys associated with a given programming language may require any one operator to alternate a plurality of fonts at the computer-linked typewriter console; however, as is well known, each font relates to a different layout of keyboard characters.
As font changes occur, it has been proposed to employ key buttons, each bearing a plurality of characters to aid the observer-user in more efficiently using the typewriter console. It has been further proposed to fit the key buttons with adjustable plates bearing different character indicia. However, where there are a plurality of operators-users at a common typewriter console such as found at most computer terminals, numerous alphanumeric identification plates would be needed. Therefore, the above-mentioned proposals have been found to be exceedingly awkward to implement. Also, in some cases it is desirable to "highlight" certain key buttons above those displayed at adjacent buttons owing to the importance of certain programming keys being implemented at the computer terminal. None of the prior art plates provides such features.